Auckland’s Southwestern Motorway near the airport has been closed to northbound traffic for more than two hours after a serious crash on State Highway 20.

Motorists are being asked to delay their journey or exit the motorway at SH20A or Massey Rd.

One eyewitness told Newstalk ZB cars were flipped in the crash.

A police spokesperson said the crash, involving two vehicles, was reported to authorities around 12.30pm.

 “Early indications suggest three people have received moderate injuries.”

The off-ramp is expected to be closed for some time, police said.

There is gridlock on State Highway 20. Photo / File

 “Police are advising motorists to delay travel to, and around, the area where possible and expect lengthy delays. The Serious Crash Unit has been advised.”